U.S. officials have not determined who was behind an apparent cyberattack on the social media site X that limited access to the platform for thousands of users.

Elon Musk’s X has been hit by three waves of outages since this morning, which the billionaire said was due to a cyberattack.

Tens of thousands of users reported issues using Musk’s platform, formerly known as Twitter, after what appeared to be an earlier outage.